Known air conditioning systems used in transport vehicles, such as commercial aircraft, typically use an air-based thermodynamic cycle to provide cool, pressurized air to various interior compartments of the aircraft, such as a passenger cabin, cargo compartments, and the like. The known air conditioning systems are typically powered pneumatically by bleed air extracted from the compressor stages of vehicle engines, such as a gas turbine engine of an aircraft. The bleed air from the engine is at an elevated temperature and pressure. The air conditioning systems typically use ram air from the ambient environment outside of the vehicle to cool the bleed air. Once the bleed air is cooled and conditioned in the air conditioning system, the bleed air is then used for various vehicle cooling tasks. For example, the bleed air may be distributed into the passenger cabin for temperature control, ventilation, and pressurization within the passenger cabin. After flowing through the passenger cabin, the air can be discharged to the ambient environment through exhaust ports and/or valves.
However, the use of bleed air from the engine or other bleed air source for air conditioning diverts power that could otherwise be used for propulsion. For example, using bleed air to cool and condition the passenger cabin may reduce fuel economy and/or efficiency during operation of the vehicle because work is expended to generate the high pressure air that is not used for propulsion.
Furthermore, using ram air from outside the vehicle to cool the bleed air typically requires capturing ambient air and directing the ambient air into the vehicle through air intakes or vents. Directing air into the vehicle during movement of the vehicle for cooling the bleed air increases drag on the vehicle (relative to directing less ambient air into the vehicle). The increased drag may reduce fuel economy and efficiency because more energy may be needed to propel the vehicle through the ambient environment at a given velocity.